Guide means for induction heating coil

ABSTRACT

In an induction heating installation including a generally fixed multi-turn induction heating coil having a central workpiece receiving passageway wherein the guide means through the passageway includes a bridge supported on opposite ends of the passageway and externally of the coil.

United States Patent [1 1 Jensen GUIDE MEANS FOR INDUCTION HEATING COIL [75] Inventor: Fred C. Jensen, Euclid, Ohio [73] Assignee: Park-Ohio Industries, Inc.,

Cleveland, Ohio [22] Filed: Nov. 21, 1972 [21] Appl. No.: 308,398

[52] US. Cl....' 219/10.67, 219/1079 [51] Int. Cl. 1105b 5/08 [58] Field of Search 219/1067, 10.69,

[56] References Cited UNITED STATES PATENTS 2/1957 Brogan 2l9/10.67

[ Nov. 20, 1973 2,950,374 8/1960 Lombard 219/1067 2,819,370 1/1958 Osborn 219/1067 FOREIGN PATENTS OR APPLICATIONS 663,080 5/1963 Canada 219/1067 Primary Examiner-Bruce A. Reynolds Attorney-James H. Tilberry et al.

[57] ABSTRACT In an induction heating installation including a generally fixed multi-tum induction heating coil having a central workpiece receiving passageway wherein the guide means through the passageway includes-a bridge supported on opposite ends of the passageway and externally of the coil.

11 Claims, 6 Drawing Figures PATENIEU NOV 20 I975 SHEET 1 CF 3 GUIDE MEANS FOR INDUCTION HEATING COIL This invention relates to the art of induction heating and more particularly to a guide means for an induction heating coil of the type employing a multi-turn coil.

The invention is particularly applicable for an induction heating device of the type employing a multi-tum induction heating coil having a central workpiece receiving passageway through which elongated workpieces are forced; however, it is appreciated that the invention has much broader applications and may be used in various other induction heating devices employing multi-turn indication heating coils having a central workpiece receiving passageway.

When heating billets or other relatively heavy workpieces which may weigh as much as 500 pounds and must be heated to high temperatures as high as approximately 2,300F, it is common to provide a multi-turn induction heating coil having a central, longitudinally extending workpiece receiving passageway through which the billets are pushed successively for induction heating. These multi-turn induction heating coils are generally encapsulated in an insulating material and have an internal ceramic lining to prevent damage to the coil from the heat created within the workpiece during the heating operation. While the workpieces are being pushed through the coil they can not rest upon the relatively weak or fragile ceramic lining. Consequently, it is common practice to place within the coil two or more longitudinally extending rails or guide means for supporting the workpieces as they are within the coil. These rails also position the workpieces for proper magnetic coupling with the coil. Since the rails are generally supported by the ceramic, damage to the ceramic liner often occurs. This requires replacement of the rails and repair of the ceramic. When a low frequency, such as 50 or 60 cycles per second, is used in the heating operation, the workpiece can vibrate which causes increased propensity to damage the guide rails. For these reasons, prior devices for heating workpiece moving through a multi-turn coil have required a substantial amount of servicing during prolonged use. It has been suggested to use more rails in the coil or increase the size of the rail to prevent this damage. This often resulted in an unwanted increase in the spacing between the workpiece and the induction heating coil, especially in the area of the support rails.

The present invention relates to an improvement in the guide means for a coil of the type explained above which improvement overcomes the above-mentioned disadvantages and others and results in an induction heating installation which substantially reduces the maintenance resulting from damage to the guide means extending through the multi-tum coil.

In accordance with the present invention, there is provided an improvement in an induction heating installation of the general type described above, which improvement includes a first support element adjacent one end of the coil, a second support element adjacent the other end of the coil, and a bridge element extending between the support elements and through the passageway of the coil so that the actual support means for the workpiece does not come in pressure transmitting contact with the internal portion of the coil. This precludes fatigue damage to the lining of the coil or physical damage to the lining and guide means caused by movement of the workpiece into and out of the coil.

The primary object of the present invention is the provision of an improved guide means for a multi-tum induction heating coil, which improvement includes a bridge extending through the coil and supported on opposite ends of the coil.

Another object of the present invention is the provision of an improved induction heating installation using a multi-tum induction heating coil which improvement substantially reduces the maintenance resulting from damage to the guide means and the liner of the coil.

These and other objects and advantages will become apparent from the following description taken together with the accompanying drawings in which:

FIG. 1 is a parially, cross-sectional side elevational view showing the preferred embodiment of the present invention;

FIG. 2 is a cross-sectional view taken generally along line 22 of FIG. 1;

FIG. 3 is an end view taken generally along line 3-3 of FIG. 1;

FIG. 4 is an end view taken generally along line 4-4 of FIG. 1;

FIG. 5 is a cross-sectional view taken generally along line 55 of FIG. 1; and,

FIG. 6 is a view similar to FIG. 5 illustrating a modification of the preferred embodiment of the present invention.

Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only, and not for the purpose of limiting same, FIGS. 1 and 2 show an induction heating installation A for inductively heating a series of workpieces B as they pass through a multi-turn induction heating coil C connected by leads 10, 12 to an appropriate source of alternating current, such as schematically represented generator 20.In a preferred embodiment, the workpiece B is progressed through the coil from right to left during the heating operation. It is appreciated that the workpiece could be inserted and removed from one end of the coil without departing from the spirit and scope of the present invention. To support the workpiece within the coil C, there is provided an improved guide means D which forms the essence of the present invention and will be described later in detail.

Referring now to the coil C, this coil is generally encapsulated within an insulating material which has been omitted for the purposes of simplicity. The coil is positioned in a horizontal direction and has a central workpiece receiving passageway 30 in which there is located a ceramic casing or lining 32 defining an internal surface 34. The coil is mounted by an appropriate mounting means which may take a variety of structural forms; however, in accordance with the illustrated embodiment of the present invention, spaced compression plates 40, 42 having workpiece openings 44, 46 are used to support the coil. Of course, these plates are appropriately positioned in a fixed manner at the proper location for the heating installation. Upper tie rods 50, 52 having heads 50a, 52a are used to fix the upper portion of the plates 40, 42 in their proper position with respect to coil C. The ends of the tie rods receive nuts 50b, 52b for compressing the liner 32 between the plates. Ina like manner, lower tie rods 54, 56 provided with nuts 54a, 56a compress the lower portion of plates 40, 42 into position for rigidifying the total installation. As so far explained, the induction heating installation does not differ from standard installations. By energizing the coil C workpieces passing through the coil are inductively heated for subsequent processing.

In accordance with the invention, there is provided the improved guide means D which essentially provides a bridge extending through the workpiece receiving passageway 30 and spaced from internal surface 34 so that a workpiece passing through the coil does not come into engagement with any portion of the coil or exert forces on the liner 32. To accomplish this, there is provided a bridge 60 forming a catenary span through the coil and supported on opposite ends of the coil by a structure not forming a part of the coil assembly itself. Consequently, no force is applied to the ceramic lining 32 or the coil during processing of the workpiece. The bridge 60 is formed from tubular metal so that cooling can be provided, and the bridge has a series of structural elements to rigidify the bridge for support of the workpiece. This structure can take a variety of forms to satisfy these purposes; however, in accordance with the preferred embodiment of the present invention, bridge 60 includes two lower spaced rails 62, 64. Rail 64 has a coolant inlet 70 and a coolant outlet 72. Although not shown, rail 62 also has similar inlets and outlets so that coolant can be continuously circulated through these rails for the purpose of cooling the same and maintaining a low temperature for the rails.

The lower spaced rails are supported in spaced relationship by a lower serpentine support beam 80 extending back and forth between the lower rails and including a coolant inlet 82 and a coolant outlet 84. To further rigidify the bridge 60, side rails 90, 92 extend upwardly from the lower spaced rails 62, 64, respectively. These side rails are formed from upper rails 94, 96 which are secured to the lower rails 62, 64, respectively, at opposite ends and extend upwardly above these lower rails to form rigidifying truss type of structures. Upper rail 94 has a coolant inlet 100 and a coolant outlet 102. In a like manner, upper rail 96 has a coolant inlet 104 and a coolant outlet 106. Between the upper rails and the lower rails there is provided spaced serpentine beams 110, 112. These beams have portions oblique to the upper and lower rails as well as perpendicular portions. This provides a rigidified side rail structure for somewhat preventing extensive bowing of the catenary portion of bridge 60 as it extends through the coil C and supports a workpiece. Serpentine beam 112 has a coolant inlet 120 and a coolant outlet 122. In a like manner, the other serpentine beam of the side rails has provisions for inlet and outlet of coolant; however, this is not shown in the drawings. To actually support the workpiece as it is moved along bridge 60, the bridge is provided with a lower support rail 130 having two transversely spaced coolant tubes 132, 134. Tube 132 has an inlet 140 and an outlet 142. In a like manner, tube 134 has an inlet 144 and an outlet 146. The lower support rail 130 is formed from wear resistant material and supports the workpiece on the bridge 60 as the workpiece is within the coil itself. To prevent damage to the side rails 90, 92, there are provided two side wear plates 150, 152, best shown in FIGS. 3-5. These side plates include coolant tubes 160 having inlets 162 and outlets 164.

It is appreciated that the catenary bridge 60 extending through the induction heating coil is a relatively rigid structure which may be made from metal tubing. By maintaining the structures therein cool by appropriate circulation of coolant, the strength of the material remains high and there is little effect upon the heating operation. In addition, the low mass of the bridge precludes detrimental effect to the heating operation. By constructing the bridge 60 from a series of elements as described, there is no well defined current path; therefore, circulation of currents through the bridge itself is somewhat precluded.

As previously mentioned, the bridge 60 is supported on the opposite ends by structural arrangements external of the coil C. In accordance with the illustrated embodiment of the present invention, this is accomplished by a first bridge support device and a second bridge support device 172. Referring now to the bridge support device 170, there is included a transversely extending bar secured onto a downwardly extending plate 182, as best shown in FIGS. 1, 2 and 3. Plate 182 is locked onto tie rods 54, 56 by nuts 184, 186. This holds the plate 182 rigidly with respect to a coil mounting means. The use of the bar 180 and plate 182 prevents twisting of bridge 60 in a transverse direction and holds the right end of the bridge in a rigid manner. The rigid connection also prevents longitudinal movement of bridge 60 at the first support device 170.

Referring now to the second bridge support device 172 as best shown in FIGS. 1, 2 and 4, this support device includes a heavy plate having apertures 192, 194 that receive insulating sleeves 196. Tie rods 54, 56 extend through the sleeves 196 so that the plate 190 can move in a direction away from the nuts 54a, 56a. The insulation sleeves 196 form an electrical insulation between plate 190 and the coil support means. In this manner, there is no circulating current through the bridge and through the tie rods 54, 56. Thus, the bridge 60 does not form a completed electrical circuit or turn which could cause a transformer action. Nuts 200, 202 on tie rods 54, 56 are spaced a distance a from plate 190 in its normal position. This allows a certain amount of expansion of bridge 60 during the heating operation. It is noted that the workpiece B is moved from right to left in FIGS. 1 and 2. Support device 170 is fixed at the end of the bridge which is in tension. Consequently,

any elongation of the bridge due to frictional drag by movement of the workpiece around the bridge is allowed by the spacing a between the nuts 200, 202 and plate 190. Consequently, the bridge support devices 172 allow for thermal expansion of the bridge as well as expansion caused by movement of the workpieces through the coil C. It is noted that the allowed movement is in only the longitudinal or horizontal direction. The support device 172 precludes transverse twisting of the bridge 60 or transverse movement of any type with respect to the tie rods 54, 56. In this manner, the bridge remains relatively flat during the heating operation. This tends to prevent undue warpage of the bridge. It is noted that the bar 180, plate 182 and plate 190 have a relatively large size with respect to the tubing forming the bridge 60. This is to increase the holding tendency of these support elements.

Referring now toFIG. 6, a further modification of the present invention is illustrated. In this instance, the guide means D includes a bridge 60'. This bridge is primarily constructed in accordance with the previous description of bridge 60; therefore, details of the bridge structure is omitted for the purpose of simplicity. The bridge 60' includes two spaced support rails 210, 212 which are positioned on opposite sides of a fixed rail 214 secured to the ceramic lining 32 in a manner similar to previous construction of guide rails extending through a multi-turn coil. Bridge 60 is supported on opposite ends of the coils by a structure similar to that shown in FIGS. 1 and 2; however, the total bridge and support structure is allowed to be moved in a vertical direction between two positions and also in a horizontal direction. This can be done by separating the tie rods 54, 56 from the coil support structure and allows them to be movable vertically and horizontally by an appropriate drive arrangement well known in the walkingbeam type of conveyors. Additional lower tie rods are then provided to compress liner 32. As the bridge 60' is moved upwardly, the workpiece B is supported on rails 210, 212. When this happens, the bridge 60 is moved in a forward direction and then lowered. This deposits the workpiece B at an advanced position on the center fixed rail 214. Bridge 60 in its lowered position is then moved rearwardly. The process is repeated at a rate sufficient to move the workpiece through the coil C during the induction heating operation. This structure adapts the concept of bridge 60' to the walking beam concept sometimes employed in heating of relatively large workpieces in multi-turn induction heating coils to prevent friction drag on the workpiece supporting structure.

Having thus defined my invention, I claim:

1. In an induction heating installation including a generally fixed multi-turn induction heating coil having first and second axially spaced ends and a central workpiece receiving passageway with afirst end adjacent said first coil end and a second end adjacent said second coil end, mounting means for supporting said coil with said passageway extending in a generally horizontal direction, and guide means extending within said passageway for supporting a workpiece as it is within said horizontally extending workpiece receiving passageway, the improvement comprising: said guide means comprising a first support element adjacent said first end of said passageway and spaced outwardly from said first coil end; a second support element adjacent said second end of said passageway and spaced outwardly from said second coil end; a bridge element extending through said passageway and including first and second horizontally spaced support portions separated by a catenary portion; means for securing said first support portion to said first support element; and,

means for securing said second support portion to said second support element whereby said catenary portion extends between said first and second coil ends.

2. The improvement as defined in claim 1 including means for allowing longitudinal movement of said second support portion with respect to said second support element.

3. The improvement as defined in claim 1 including means for preventing transverse movement of said first support portion with respect to said first support element.

4. The improvement as defined in claim 3 including means for preventing transverse movement of said second support portion with respect to said second support element.

5. The improvement as defined in claim 1 including first securing means for securing said first support element onto said mounting means and second securing means for securing said second support element onto said mounting means.

6. The improvement as defined in claim 5 wherein one of said securing means includes means for electrically isolating said one securing means from said mounting means.

7. The improvement as defined in claim 1 wherein said bridge element includes a pair of horizontally extending rods and support beams extending between said rods.

8. The improvement as defined in claim 7 wherein said rods include central coolant passages and means for directing a coolant through said passages.

9. The improvement as defined in claim 7 including a side rail extending upwardly from each of said rods.

10. The improvement as defined in claim 9 wherein each of said side rails includes an upper rod and beams extending at oblique angles between one of said horizontally extending rod and said upper rod.

11. The improvement as defined in claim 1 including lifting means for allowing vertically upward movement of said guide means between a first and second position, means for moving said guide means in a horizontal direction and a fixed support member extending longitudinally through said passageway, said member having a vertical height for receiving a workpiece only when said lifting means is in said first position. 

1. In an induction heating installation including a generally fixed multi-turn induction heating coil having first and second axially spaced ends and a central workpiece receiving passageway with a first end adjacent said first coil end and a second end adjacent said second coil end, mounting means for supporting said coil with said passageway extending in a generally horizontal direction, and guide means extending within said passageway for supporting a workpiece as it is within said horizontally extending workpiece receiving passageway, the improvement comprising: said guide means comprising a first support element adjacent said first end of said passageway and spaced outwardly from said first coil end; a second support element adjacent said second end of said passageway and spaced outwardly from said second coil end; a bridge element extending through said passageway and including first and second horizontally spaced support portions separated by a catenary portion; means for securing said first support portion to said first support element; and, means for securing said second support portion to said second support element whereby said catenary portion extends between said first and second coil ends.
 2. The improvement as defined in claim 1 including means for allowing longitudinal movement of said second support portion with respect to said second support element.
 3. The improvement as defined in claim 1 including means for preventing transverse movement of said first support portion with respect to said first support element.
 4. The improvement as defined in claim 3 including means for preventing transverse movement of said second support portion with respect to said second support element.
 5. The improvement as defined in claim 1 including first securing means for securing said first support element onto said mounting means and second securing means for securing said second support element onto said mounting means.
 6. The improvement as defined in claim 5 wherein one of said securing means includes means for electrically isolating said one securing means from said mounting means.
 7. The improvement as defined in claim 1 wherein said bridge element includes a pair of horizontally extending rods and support beams extending between said rods.
 8. The improvement as defined in claim 7 wherein said rods include central coolant passages and means for directing a coolant through said passages.
 9. The improvement as defined in claim 7 including a side rail extending upwardly from each of said rods.
 10. The improvement as defined in claim 9 wherein each of said side rails includes an upper rod and beams extending at oblique angles between one of said horizontally extending rod and said upper rod.
 11. The improvement as defined in claim 1 including lifting means for allowing vertically upward movement of said guide means between a first and second position, means for moving said guide means in a horizontal direction and a fixed support member extending longitudinally through said passageway, said member having a vertical height for receiving a workpiece only when said lifting means is in said first position. 